Enterovirus 71 Can Directly Infect the Brainstem via Cranial Nerves and Infection Can Be Ameliorated by Passive Immunization

Abstract

Enterovirus 71 (EV71)-associated hand, foot, and mouth disease may be complicated by encephalomyelitis. We investigated EV71 brainstem infection and whether this infection could be ameliorated by passive immunization in a mouse model. Enterovirus 71 was injected into unilateral jaw/facial muscles of 2-week-old mice, and hyperimmune sera were given before or after infection. Harvested tissues were studied by light microscopy, immunohistochemistry, in situ hybridization, and viral titration. In unimmunized mice, viral antigen and RNA were detected within 24 hours after infection only in ipsilateral cranial nerves, motor trigeminal nucleus, reticular formation, and facial nucleus; viral titers were significantly higher in the brainstem than in the spinal cord samples. Mice given preinfection hyperimmune serum showed a marked reduction of ipsilateral viral antigen/RNA and viral titers in the brainstem in a dose-dependent manner. With optimum hyperimmune serum given after infection, brainstem infection was significantly reduced in a time-dependent manner. A delay in disease onset and a reduction of disease severity and mortality were also observed. Thus, EV71 can directly infect the brainstem, including the medulla, via cranial nerves, most likely by retrograde axonal transport. This may explain the sudden cardiorespiratory collapse in human patients with fatal encephalomyelitis. Moreover, our results suggest that passive immunization may still benefit EV71-infected patients who have neurologic complications.

In Vivo Imaging with Bioluminescent Enterovirus 71 Allows for Real-Time Visualization of Tissue Tropism and Viral Spread

“…This work may add to our understand-blood-brain barrier; however, alteration of blood-brain barrier permeability as a result of proinflammatory cytokines, such as tumor necrosis factor, interleukin-1␤ (IL-1␤), and IL-6, may allow nAbs to enter the CNS parenchyma (36). Recent findings also showed that treatment with antibodies after infection with EV71 led to decreases in clinical signs of disease and viral loads in the brains of infected mice (37). We detected nAbs in AG129 mice at 35 and 56 dpi.…”

A monoclonal antibody to ameliorate central nervous system infection and improve survival in a murine model of human Enterovirus-A71 encephalomyelitis

“…Since both skeletal muscles and the CNS were infected in most murine models of EV-A71 infection, the observed limb weakness/paralysis in infected animals could be due either to myositis and/or CNS infection Tan et al, 2014). Hence, we believe a more objective way to assess the effectiveness of passive immunization to ameliorate CNS infection is to determine the response to treatment by histopathology and viral quantification as well as by limb weakness/paralysis.…”

“…L-hSCARB2 cells, a mouse fibroblast cell line that expresses the EV-A71 binding and entry receptor, human scavenger receptor class B member 2 (SCARB2) (Yamayoshi et al, 2009) was grown in DMEM supplemented with 5% FBS and 5 mg/ml puromycin (Yamayoshi et al, 2009) (obtained from Dr. Koike, Tokyo Metropolitan Institute of Medical Science). All viruses used in this study (Table 1) were cultured and titrated using Vero cells as described previously Tan et al, 2014).…”

“…Several studies have previously shown that hyperimmune sera or monoclonal antibodies (MAb) containing EV-A71-specific neutralizing antibodies were able to protect experimentallyinfected mice from disease (Ng et al, 2015;Tan et al, 2014). Recently, we described the effective use of a single optimal dose of hyperimmune serum to prevent and ameliorate CNS infection in a murine model of EV-A71 encephalomyelitis (Ong et al, 2010;Tan et al, 2014).…”

“…Recently, we described the effective use of a single optimal dose of hyperimmune serum to prevent and ameliorate CNS infection in a murine model of EV-A71 encephalomyelitis (Ong et al, 2010;Tan et al, 2014). However, the use of hyperimmune sera for passive immunization studies has several disadvantages compared to monoclonal antibodies, including poor reproducibility due to batch-to-batch variability of neutralizing antibody production and specificity.…”